Device which can be applied in bone and/or tissue in the human body, and method and use of said device

ABSTRACT

A device, for example in the form of an implant, is arranged to be applied via at least one surface or one portion (for example an outer portion) to bone and/or tissue in the human body. An agent which stimulates bone growth, in the form of HA, is used in connection with the device. The device, the surface or the portion comprises or consists of compressed bone-compatible and/or tissue-compatible material in the form of titanium powder. The titanium powder is mixed with the agent, which is also in powder form, and a composite material is formed with the two powders by means of impact compaction. The invention also relates to a method and use in connection with devices of the type in question. A novel type of HA use is made possible and eliminates, inter alia, the disadvantages of loosening HA layers during production of the device.

The present invention relates inter alia to a device which, via at leastone surface or one portion, is arranged to be applied in bone and/ortissue in the human body, for example jaw bone. The device is provided,at the surface or portion, with an agent which stimulates bone growth,which can be HA (hydroxyapatite). In addition, at least a part bearingthe surface, or the portion, comprises or consists of compressedbone-compatible and/or tissue-compatible powder material, preferablytitanium powder. The invention also relates to a method for producingthe device in question, which can, for example, be an implant. Theinvention moreover relates to a use in connection with the production ofthe device.

It is already known to produce dental crowns, for example, made oftitanium powder which is compacted to a great density, for example by asintering method. In this connection, reference may be made, inter alia,to PCT application WO 00/15137 from the same Applicant as the presentpatent application. In connection with implants, it is also alreadyknown to use a bone-growth-stimulating agent, for example in the form ofHA. Reference may be made to the patent literature and inter alia to thepatents obtained and the patent applications filed by the sameApplicant. In the prior art, it has been proposed to apply HA in layerson the outside of the implant or the like in question. The underlyingidea is that the surface layers exposed to the bone or tissue willfacilitate the incorporation of the implant or the like.

In connection with the known arrangements and methods, there is aproblem in ensuring that the HA layers remain in place, for exampleduring after-treatment of the implant or the like. There is therefore aneed for a solution to the problems of the layers coming loose. The mainobject of the present invention is to solve this problem among others.In accordance with the concept of the invention, a composite materialwill be created between titanium (Ti) and hydroxyapatite (HA), where theHA is present as particles or fractions admixed in the titanium bulk orthe titanium body. By creating a bulk composite, the latter can be usedas a raw material for subsequent working of the components in question,without the aforementioned problems of the loosening of the layers ofHA. The underlying idea is generally that the HA particles or HAfractions in the surface layer are exposed to the bone and/or tissue andthereby facilitate incorporation of the titanium implant.

In normal pressureless sintering of titanium powder mixed with finelyparticulate HA powder, these react and form new phases. If a samplesintered in this way is exposed to heat, swelling may occur. There aremethods available which are intended to allow these materials to besintered together without creating any appreciable reactions, but thesemethods are relatively sophisticated and expensive, for example HIP (hotisostatic pressing) or SPS (spark plasma sintering). There is thereforea need for alternatives to these sintering methods. The invention alsohas the object of solving these problems.

The feature which can principally be regarded as characterizing thedevice mentioned in the introduction is that the powder material and thebone-growth-stimulating agent form a composite material which isobtained by means of impact compaction and, if appropriate, subsequentsintering.

In further developments of the inventive concept, thebone-growth-stimulating agent (HA) can be arranged completely orpartially in or at the actual surface layer and can thus be exposed tothe bone and/or tissue in question. The agent can be chosen withparticle sizes or fractions in the range of 90-120 μm. The titaniumpowder which is used will preferably have a considerable purity, forexample a purity of 99.99%, and a relatively small particle size. By wayof example, titanium powder in the form of Wah Chang HP (or CP) −325Mech T080014 (010607) can be included in the composite structure.Titanium powder in a quantity of ca. 90-98%, preferably ca. 95%, and HApowder in a quantity of 2-10%, preferably ca. 5%, form the startingmaterial for the composite material compacted by impaction and possiblesintering. The last-mentioned percentage figures are chosen so as togive a total quantity of 100%.

A method according to the invention can be regarded as beingcharacterized principally by the fact that the mixing together of thebone-compatible and/or tissue-compatible powder material and of saidagent which is in powder form takes place in a first step. This isfollowed by application of the mixture in one or more mold cavitiesbelonging to a mold applied in a machine which effects impact compactionand which has properties allowing it to operate with a high impactcompaction energy. This is followed by activation of the impacting unitof the machine so that it acts on the mold and transfers the energy tothe powder mixture and thereby creates a blank for the device. Finally,the blank is treated in one or more treatment units for producing thedevice from the blank. In said treatment steps, the blank can besintered and/or heat-treated and subjected to a treatment or treatmentsof various types, for example chemical, electrochemical and/ormechanical treatment or machining, for example milling, turning,shot-peening, etc. The machine can be of a kind known per se and is inthis case of the type which generates an impact compaction energy of ca.335 Nm or higher. The machine can operate with one or more impactsagainst the mold, and the same amounts of energy or different amounts ofenergy can be used in the different impacts. The titanium particles arecompressed to a substantial density, for example 98% or more. Thepositions of the HA particles in the composite material can becontrolled upon mixing and application in the mold cavity of the mold.When the blank is machined to give a finished device or finished surfaceor finished portion, a desired quantity of HA particles will be presenton the surface exposed to the bone and/or tissue in question.

A use according to the invention can be regarded as being principallycharacterized by the fact that an impact-type compaction machine with ahigh impact compaction energy is used to compress the powder materialand said agent in powder form to give a composite material. By means ofwhat has been proposed above, a device is obtained which is efficientand is simplified from the point of view of use, and a simplified methodis obtained. Highly compressed composite bodies can be obtained with theaid of impact compaction (high-velocity compaction). Tests have beencarried out on producing a composite material of said type and density,after sintering has been carried out, by cutting up cross sectionalsurfaces and studying the microstructure and interfaces between titaniumand HA.

In said tests, small amounts of the two powders were weighed-in on ananalysis balance and mixed in a beaker at 95.00% titanium and 5.00% HA.The powders were mixed in the dry state by brief agitation and stirring.

The powder mixture was impact-compacted at Hydropulsor in Karlskoga in amodified cutting machine “Hydropulver Hyp 30-15”. The powder was placedin a cylindrical, 14-mm press tool of steel lubricated with MOS₂. Thepowder weight per block was 2.0 g. Five impacts in succession were madeagainst the powder (each block) with 335 Nm energy on each impact. Fivesuch blocks were produced.

The green density was measured with a micrometer screw and with theArchimedes principle in distilled water (without vacuum). Both themeasurements gave the same result for the green density. The sampleswere cut in two in water with a low-speed cut in order to obtain twosamples (a+b).

Some of the samples were then heat-treated in vacuum (NB Pp10) inaccordance with the following: Sample Ramp ° C./min Temperature ° C.Holding time (min) 1a 10 700  60 1b 10 900  6 2a 10 500 600 2b Greenbody Green body Green body 3a — — — 3b — — — 4a — — — 4b — — — 5 — — —

The samples lay on Mo wire on Ti plate in Mo-degel. “Sintered” densitywas also measured using the Archimedes principle without vacuumdirectly, after which the samples were dried in a heating chamber at100° C. for 0.5 h. The densities below may be slightly higher as Ha hasa certain porosity which is not taken into calculation.

The results obtained were: Temp./Holding Green density Sintered densitySample time g/cm³/% theory g/cm³/% theory 2a (2.) 500° C., 10 h4.338/98.21 4.374/99.02 1a (1.) 700° C., 1 h 4.340/98.26 4.378/99.13 1b(1..) 900° C., 0.1 h 4.340/98.26 4.380/99.17 2b (2) Green body4.338/98.21 — 3a — 4.340/98.26 — 3b — 4.340/98.26 — 4a — 4.337/98.18 —4b — 4.337/98.18 — 5 (not — 4.324/97.91 — cut)

The results were examined and the following facts elucidated:

Green body: The titanium particles had been compressed to a very highdensity and surrounded the HA particles almost completely. No grainboundary pores were visible, or only very small ones. The titaniummatrix appeared in principle as a dense material. The heat treatments atall of the tested temperature and time conditions had affected themicrostructure and had probably caused the titanium particles to growtogether, more significantly the higher the temperature used. The HAparticles appeared unaffected at all the temperatures tested. However, athin gap was observed between the titanium matrix and the HA particlesof the heat-treated samples which seemed to increase with thetemperature. At 500° C., the gap was scarcely visible (0-0.1 μm). At700° C., it was found around the HA particles and was ca. 0.2 μm wide.At 900° C, the gap was more noticeable and was ca. 0.4 μm wide. The gapcan still be considered small in view of the fact that the HA particleswere ca. 100 μm in diameter and still held firm by surfaceirregularities and the tight-fitting titanium matrix.

A 98% compressed (unsintered) composite material of titanium powder andhydroxyapatite was produced by impact compaction.

The compression effect was observed throughout the sample body. Thetitanium matrix surrounded the HA particles.

The composite was heat-treated with the aim of binding the titaniumparticles to one another. The density increased to ca. 99%. Themicrostructure is already changed at 500° C., and more so at a highertemperature.

No reaction product between Ti and HA was observed visually in any ofthe samples, but a thin gap formed between the materials at hightemperature. However, this gap was considered small in relation to theparticle size of HA.

A presently proposed embodiment of a device, method and use will bedescribed below with reference to the attached drawings in which

FIG. 1 shows, in different enlargements, the microstructure of compositematerial which has been compacted by impaction and has not thereafterbeen exposed to heat treatment,

FIG. 2 shows, in different enlargements which correspond to theenlargements in FIG. 1, the microstructure of composite material whichhas been compacted by impaction and has thereafter been exposed to heattreatment at 500 degrees for 10 hours,

FIG. 3 shows, in a vertical view and diagrammatically, an implant in ajaw bone,

FIG. 4 shows, in a vertical view, parts of threads on an implant, and

FIG. 5 shows, in a vertical view and diagrammatically, a flow chart forproduction of a device in question.

FIG. 1 shows a microstructure of a green body Ti-HA5 with polished crosssection of an impaction-compacted cylinder. The eight differentsubsidiary FIGS. a-h show different degrees of enlargement of HAparticles applied in titanium in accordance with the above. Theleft-hand FIGS. a-d show optical images of HA particles in lightconfigurations. FIGS. e-h show HA particles in dark configurations inthe titanium. As will be seen from the figures, the titanium particleshave been compressed to a very high density and surround the HAparticles almost completely, except on the outside of the surface whichis exposed to the bone or tissue in question. The HA particles are shownin different sizes and thus, for example, FIG. d shows the interfacebetween a particle and the surrounding titanium. As can be seen from thefigures, the HA particles can be considered as forming a pore system inthe surface toward the bone or tissue. By means of this arrangement, aragged outer surface can be considered to be present on the titaniumbody if the HA particles have come loose and have migrated over to thebone or tissue structure. This therefore increases the possibilities ofsecure incorporation of the implant or the like in the bone or tissue.The optical images are taken with a camera to show how the materiallooks (white particles in a metal matrix). The SEM-EDS images show themicrostructure. On the SEM images, the HA particles are instead dark.

FIG. 2 shows corresponding enlargements of the microstructure in thecomposite material. In this case, the composite material has beenheat-treated at 500° C. for 10 hours. For comparison of FIGS. 1 and 2,reference is made to the above analysis of results.

In FIG. 3, a jaw bone is indicated diagrammatically by 1. A hole orrecess has been made in a manner known per se in the jaw bone to receivean implant 3 which can be of the type which has an external thread 4 bymeans of which the implant can be screwed into the hole 2. The implantcan have a configuration already known per se and will therefore not bedescribed in detail here.

FIG. 4 shows parts of a thread structure 5 which can be arranged on theimplant 3 in FIG. 3. In accordance with the present invention, theactual outer surface 5 a, or rather a part or portion 5 b bearing theouter surface, is made of the composite material discussed above. Thewhole implant body or the outer surface(s) or portion(s) facing the bone1 or tissue can be made of said composite material.

In FIG. 5, the impact-type compaction machine discussed above isindicated by 6. As the machine is well known per se, it will not bedescribed in detail here, except to note that the machine comprises adie 7 which is provided with a recess 8 in which two stamps 9 and 10 canextend and in which an elastic mold 11 can be arranged. The mold made ofelastic material is arranged to transmit the two-dimensional impactenergy obtained via the stamps 9 and 10 to the powder mixture which canbe placed in a diagrammatically indicated mold cavity 12 so as to give athree-dimensional product, for example said implant 3 according to FIG.3. The powder mixture has been indicated by 13 in FIG. 5. The elasticmold is provided with punch members and mold cavity. The arrangement ismoreover such that an isostatic function or isostatic action arisesagainst the powder mixture, the result being that pressing forces, forexample F1, F2, arise uniformly around the whole mold cavity and thepowder mixture. In the present case, the stamps 9 and 10 operate towardand away from one another, with the mold 11 lying in between them. Theinternal punch arrangement of the mold is not shown in FIG. 5. Theprinciples of this are shown in the Swedish patent application“Arrangement, device, method, product and use in connection with a blankmade preferably of titanium powder and intended for a dental crown orother product for the human body” filed by the same Applicant on thesame day as the present patent application. In a mixing unit 14, thetitanium powder 15 and the HA powder 16 are mixed together in accordancewith the above. The mixed-together powders are brought to the cavity 12in the mold 11 and have been indicated by 13 in accordance with theabove. The mold 11 comprises a top mold and a bottom mold which can beseparated from one another and put together. The mold 11 with punch andpowder is then transferred to the machine 6, of which one stamp 9, forexample, can be removed from the recess 8 in order to allow the mold tobe fitted. The machine is provided with a control unit 17 which can havea control panel 18. By means of the control unit, control signals 11 aregenerated for controlling the machine's movement/impact, kinetic energy,number of impacts, etc. When the machine's impacting unit is activated,the mold or molds 11 are acted upon so as to transfer the impact energyto the powder mixture and in this way create a blank/raw material. Afterthe treatment or production in the machine 6, the raw material 19 istransferred to one or more subsequent treatment steps 20, 21, etc. Intreatment step 20, the raw material 19 can be subjected to heattreatment, sintering, etc. In the treatment step, the heat-treated,sintered, etc., raw material 19′ can be subjected to chemical ormechanical working, for example turning, milling, shot-peening,electro-chemical treatment to obtain an oxide layer, etc. The raw blank19′ which has been worked can then constitute an actual component, forexample the component 3 in FIG. 3. In connection with the control of themachine by means of the control unit 17, control signals i2 can beestablished for producing different layers and/or positions of the HAparticles so that at least some of these, preferably the majority ofthem, are exposed outward from their actual surface 19″ which isintended to face toward the actual bone or tissue. In FIG. 5, a numberof layers of said type have been indicated by 22, 23 and 24. When theimplant 3 is applied in the jaw bone (see FIG. 3), the HA particles orthe HA fractions have the possibility of migrating into the surroundingbone depending on its composition.

In accordance with the invention, therefore, an impact-type compactionmachine with a high impact compaction energy is used to compress thepowder material and said agent in powder form to give a compositematerial which can form or be included in a component which can befitted in a bone or a bone tissue in the human body. By means of theinvention, it is possible to accelerate the incorporation of the implantor the like, without ignoring the long term. The titanium powder canhave particle sizes of 20-50 μm (possibly up to 200 μm). The particlesof HA can be given a cone shape and have sizes of 10-500 μm. Sinteringtemperatures of 100-1200° C. can be used.

The invention is not limited to the above embodiment, and instead it canbe modified within the scope of the attached patent claims and theinventive concept.

1. A device which, via at least one surface or one portion, is arrangedto be applied to bone and/or tissue in the human body, for example jawbone, and which, at the surface or portion, is provided with an agentwhich stimulates bone growth, preferably HA (hydroxyapatite), where atleast one surface-bearing part or the portion comprises or consists ofcompressed bone-compatible and/or tissue-compatible material, preferablytitanium powder, characterized in that the powder material and thebone-growth-stimulating agent form a composite material which isobtained by means of impact compaction and, if appropriate, sintering.2. The device as claimed in patent claim 1, characterized in that thebone-growth-stimulating/HA agent is arranged completely or partially inor at the actual surface layer and can thus be exposed to the boneand/or tissue in question.
 3. The device as claimed in patent claim 1,characterized in that the bone-growth-stimulating agent is in the formof particulate fractions with sizes in the range of 90-120 μm.
 4. Thedevice as claimed in patent claim 1, characterized in that titaniumpowder with considerable purity, preferably a purity of 99.99%, and arelatively small particle size (Wah Chang HP (or CP) −325 Mesh T080014(010607)) constitutes the base for the composite structure.
 5. Thedevice as claimed in claim 1, characterized in that titanium powder in aquantity of ca. 90-98%, preferably ca. 95%, and HA powder in a quantityof 2-10%, preferably 5%, form the starting material for the materialcompacted by impaction and possible sintering.
 6. A method for producinga device, for example an implant, which, via at least one surface or oneportion, is arranged to be applied to bone and/or tissue in the humanbody, for example jaw bone, and which, at the surface or portion, isprovided with an agent which stimulates bone growth, preferably HA,where at least one surface-bearing part or the portion is made ofcompressed bone- compatible and/or tissue-compatible material,preferably titanium powder, the method comprising: a) mixing togetherthe bone-compatible and/or tissue- compatible powder material and saidagent which is in powder form, b) applying the mixture in a mold cavitybelonging to a mold applied in a machine which effects impact compactionand which operates with a high impact compaction energy, c) activatingthe impacting unit of the machine so that it acts on the mold andtransfers the energy to the powder mixture and thereby creates a blankfor the device, d) treating the blank in one or more treatment units forproducing the device from the blank.
 7. The method as claimed in patentclaim 6, characterized in that the blank is sintered and/or heat-treatedand is subjected to chemical, electrochemical and/or mechanicaltreatment or machining (milling, turning, shot-peening, etc.).
 8. Themethod as claimed in patent claim 6, characterized in that, in step a),titanium powder of considerable purity, for example 99.99%, andrelatively small particle size is mixed together with HA, for examplesintered HA, which has been crushed and screened to the fraction 90-120μm.
 9. The method as claimed in patent claim 8, characterized in thatthe mixture consists of ca. 95% titanium powder and 5% HA powder, andthe powders are mixed in the dry state, with agitation and stirring. 10.The method as claimed in patent claim 8, characterized in that themachine is controlled so as to generate an impact compaction energy ofca. 335 Nm or higher and to execute one or more impacts against themold.
 11. The method as claimed in claim 6, characterized in that thetitanium particles are compressed to a substantial density, for example98%, and in that there is substantial surrounding of the HA particles.12. The method as claimed in claim 6, characterized in that thepositions of the HA particles in the composite material are controlledupon mixture and application in the mold cavity of the mold, and in thatthe blank is machined so that HA particles are present at the surfaceexposed to the bone and/or tissue.
 13. Use in the production of a devicemade of compressible bone-compatible and/or tissue-compatible powdermaterial, for example titanium powder, and provided with abone-growth-stimulating agent, preferably HA, characterized in that animpact-type compaction machine with a high impact compaction energy isused to compress the powder material and said agent in powder form togive a composite material.